Nuclear Reactors and Plutonium Production ISIS Course-Week 4 October 23, 2014 Nuclear Reactors • A nuclear reactor is an apparatus or machine in which fissile material can be made to undergo a controlled, self-sustaining nuclear reaction with the consequent release of energy. The Basic Parts of a Reactor http://en.wikipedia.org/wiki/Magnox • Fuel region • Heat removal equipment • Control system • Refueling capability Purposes of Reactors • Nuclear reactors are used for civilian purposes to – generate electricity – produce heat via steam – produce isotopes for medical, industrial, or research purposes – conduct research – propel surface ships, such as ice-breakers • Nuclear reactors are also used for military purposes to – produce plutonium for nuclear weapons – produce tritium for nuclear weapons – propel military submarines and surface ships – power aircraft and rockets (abandoned) Classification of Reactors • Power reactors – typically civilian, almost all now generate electricity. Some produced steam for district heating. Typically make large quantities of reactor-grade plutonium. • Research reactors – typically civilian aimed at making isotopes or conducting research. – In non-proliferation context, ostensibly civilian research reactors have also been used to make plutonium for nuclear weapons, e.g. Cirus and Dhruva reactors in India. The misuse of the Taiwan research reactor was planned. Is the Arak reactor in Iran in this category, ostensibly a civilian research reactor but in reality it would also have produced plutonium for nuclear weapons? • Propulsion reactors – either civilian or military • Production reactors – almost always military and dedicated to plutonium and tritium production for nuclear weapons, which means that the goal is the production of weapon- grade plutonium. Reactors • Reactor types vary greatly, some are far simpler to build than others • Production reactors and research reactors are the simplest to build. • Graphite- and heavy water-moderated reactors use natural uranium fuel, so there is no need for uranium enrichment capabilities. These are usually the types sought by proliferant states to make plutonium for weapons. • Typically, commercial reactors use LEU fuels and have much more advanced control and safety systems than production reactors We will consider three types of reactors in more detail I. Production Reactors II. Research Reactors III. Power Reactors I. Production Reactors • There have been many types of production reactors, almost all of which are shut down. The few remaining operational ones are in India, Pakistan, and Israel. • Their initial goal was to make weapon-grade plutonium for nuclear weapons. Later, some also have made tritium. • They typically were designed to use natural uranium fuel. Some types, such as the Savannah River production reactors shifted to highly enriched uranium fuel in a driver/target system. • Fuel was simple, often uranium metal with simple cladding • They have been cooled by water, carbon dioxide, or even air • Moderated typically by graphite or heavy water • Some also produced electricity Hanford B Reactor: Graphite moderated, water cooled, natural uranium metal fuel http://www.hanford.gov/page.cfm/BReactor#BReactor Hanford B Reactor Initial power was 250 MWth http://www.hanford.gov/page.cfm/BReactor#BReactor Hanford B Reactor Core Face http://response.restoration.noaa.gov/about/media/restoration-amid-hanfords-nuclear-waste-and-largest-environmental-cleanup- us.html Hanford Type Reactor: The design of First Plutonium Production Reactor Source DOE French G-2 Reactors, 250 MWth each Graphite moderated, carbon dioxide fuel http://www.francetnp.fr/IMG/pdf/C-MAR_G1_G2_G3.pdf View of the G-2 reactor unit, with the fuel loading system in the foreground and the platform for the control rod winches above the reactor http://www.francetnp.fr/IMG/pdf/C-MAR_G1_G2_G3.pdf French G-2 Reactor Savannah River Production Reactor http://www.nationalregister.sc.gov/SurveyReports/HC02005.pdf Savannah River Production Reactor (K Reactor) http://nonuclear.se/deltredici.f5.k.reactr.head.html Savannah River Production Reactor Source DOE II. Research Reactors • Design and construction is relatively easy. • Some are similar to production reactors • Far simpler to build than power reactors • Fueled with LEU or HEU • Many can be used to make plutonium via a driver/target system China Advanced Research Reactor (CARR) is a tank in pool, light water cooled, heavy water reflected, near 20% LEU fuel http://www.world-nuclear-news.org/NN-Chinese_research_reactor_starts_up-1805107.html Tehran Research Reactor http://www.pbs.org/wgbh/pages/frontline/tehranbureau/2011/04/iran-plans-4-new-research-reactors-mousavi-aide-pressed-to-confess.html Tehran Research Reactor: Pool type, light water cooled and moderated http://www.nti.org/gsn/article/israel-would-not-warn-us-impending-iran-attack-official/ Arak Heavy Water Reactor http://www.isisnucleariran.org/images/gallery/arak/25Nov2009.jpg Arak Heavy Water Reactor http://en.wikipedia.org/wiki/File:Arak_Heavy_Water4.JPG Arak Heavy Water Reactor http://www.presstv.ir/detail/2013/06/12/308556/arak-reactor-under-constant-iaea-watch/ Pool Type Research Reactor http://www.ansto.gov.au/BusinessServices/OtherSpecialisedServices/Neutronactiviationanalysis/ Interior of OPAL reactor Australia III. Nuclear Power Reactors • There are many types of nuclear power reactors • The dominant types today are water-cooled and moderated, namely Pressurized Water Reactors (PWRs) and Boiling Water Reactors (BWRs). They both use LEU fuel and are expensive. • Another major type is the heavy water moderated and cooled CANDU reactor, which uses natural uranium fuel. • Older types include the Magnox reactor, advanced gas reactor, and the Russian RBMK reactor. • Breeder reactors have been built but have operated poorly. • Excluding breeder reactors, nuclear power reactors are an inefficient means of making weapon-grade plutonium, although they routinely make large quantities of reactor-grade plutonium, i.e. they discharge high burnup fuel. • However, weapon-grade plutonium production is possible, albeit inefficient, in power reactors. Overview of Major Types of Power Reactors http://www.daviddarling.info/encyclopedia/N/nuclear_reactor.htm Boiling Water Reactors https://www.asme.org/about-asme/who-we-are/engineering-history/landmarks/128-vallecitos-boiling-water-reactor Vallecitos Boiling Water Reactor Boiling Water Reactor http://www.euronuclear.org/info/encyclopedia/boilingwaterreactor.htm Pressurized Water Reactor http://che.nelson.wisc.edu/cool_stuff/energy/nuclear.shtml Pressurized Water Reactor http://www.nrc.gov/reading-rm/basic-ref/teachers/pwr-schematic.html CANDU Power Reactor http://www.cna.ca/how_works/candu_technology/ CANDU Power Reactor http://en.wikipedia.org/wiki/CANDU_reactor CANDU Power Reactor http://www.newbrunswickbeacon.ca/29433/decade-refurbishment-nightmares-point-lepreau-online/ Point Lepreau nuclear power plant CANDU Power Reactor http://www.world-nuclear-news.org/C-Restart_of_Bruce_reactor_delayed-2105124.html The turbine hall of Bruce A unit 2 (Image: Bruce Power) British Magnox Power Reactor http://www.nda.gov.uk/news/oldbury-shutdown.cfm Reactor 1 Oldbury Power Station British Magnox Power Reactor http://www.world-nuclear-news.org/RS-Fuel_transfer_to_keep_Wylfa_1_running-0908124.html Wylfa 1, the UK’s last operating Magnox reactor British Magnox Power Reactor http://en.wikipedia.org/wiki/Magnox Russian RBMK Power Reactor http://large.stanford.edu/courses/2013/ph241/kallman1/docs/nuclear_reactors.pdf Russian RBMK Power Reactor http://www.globalsecurity.org/jhtml/jframe.html#http://www.globalsecurity.org/wmd/world/russia/images/rbmk-design.gif||| Russian RBMK Power Reactor http://en.wikipedia.org/wiki/RBMK Reactor hall of the RBMK-1500 at Ignalina Nuclear Power Plant, Lithuania – the upper biological shield (UBS) lies several meters below the floor of the reactor hall. Plutonium Production in Reactors • Reactors are the principal method to make plutonium, whether deliberately or inadvertently. • The amount of plutonium produced in a reactor varies • Some reactors produce weapon-grade plutonium during normal operation; others produce reactor grade plutonium when operating normally. • All reactors can be used to make weapon-grade plutonium. Burnup of Irradiated Fuel and Plutonium Production • Burnup is a measure of the extent that uranium fuel has been irradiated in a reactor. • It is a measure of how much energy is extracted from a primary nuclear fuel source, such as uranium, via fission. It is measured both as the fraction of fuel atoms that underwent fission and as the actual energy released per mass of initial fuel. • We will use the latter, namely the amount of energy released per unit of uranium. Its units are megawatt-thermal-days per tonne of uranium, e.g. MWth-d/tonne U, MWth-d/tonne, or MWth-d/t. • Be careful not to confuse MWth with MWe. MWe measures only a fraction of the total energy produced in the reactor. • Low burnup fuel, with values such as 500-1,000 MWth-d/tonne, would typically contain weapon-grade plutonium • High burnup fuel, with values such as 30,000 MWth-d/tonne typically would contain reactor-grade plutonium. (Note: MWD/MTU is same as MWth-d/t; and MTU equates to tonnes of uranium Source of slide: DOE Plutonium (Pu) Production at Normal Burnups (grams Pu per MWth-d, here called g Pu/MWD) Source: DOE Plutonium (Pu) Production at a fixed, but low burnup, 1000 MWth-d/tonne Source: DOE Simple Approximation of Annual Weapon-Grade